Imaging for suspected appendicitis: negative appendectomy and perforation rates.

PURPOSE: To determine which patients suspected of having acute appendicitis benefit from preoperative imaging.

MATERIALS AND METHODS: The medical records of 462 consecutive patients who underwent appendectomy for clinically suspected acute appendicitis and underwent preoperative evaluation at our institution were retrospectively reviewed. Patients were divided into four groups: women (n = 166), girls (n = 46), men (n = 178), and boys (n = 72). Preoperative computed tomography (CT) or ultrasonography (US), requested by the referring clinician, was performed in 313 of the 462 patients. Unnecessary, or negative, appendectomy and perforation rates were calculated for each group for preoperative evaluation with CT, with US, and with neither CT nor US. In addition, the sensitivity and positive predictive value of CT and US were calculated for diagnosing appendicitis.

RESULTS: In women, the negative appendectomy rate was significantly lower for those who underwent preoperative CT (7% [six of 85 patients], P =.005) or US (8% [four of 49 patients], P =.019), as compared with 28% [nine of 32 patients] for those who underwent no preoperative imaging (P >.35 for all groups). The negative appendectomy rates for girls, men, and boys were not significantly affected by preoperative imaging. The sensitivity of CT and US for diagnosing acute appendicitis exceeded 93% and 77%, respectively, in all groups. The positive predictive values for both CT and US were greater than 92% in all groups.

CONCLUSION: Women suspected of having appendicitis benefit the most from preoperative CT or US, with a statistically significantly lower negative appendectomy rate than women who undergo no preoperative imaging. Therefore, we propose that preoperative imaging be considered part of the routine evaluation of women suspected of having acute appendicitis.